The Class A1 (primary contact recreation) uses are assessed (monitored) as "not supported" based on levels of indicator bacteria that exceeded state water quality criteria. The geometric means of indicator bacteria (E. coli) in the 24 samples collected during the recreational seasons of 2014 through 2016 at DNR station 10520001 near Iowa City were as follows: the 2014 geometric mean was 1288 orgs/100 ml, the 2015 geometric mean was 566 orgs/100 ml, and the 2016 geometric mean was 1028 orgs/100 ml. All three recreation season geometric means exceeded the Class A1 geometric mean criterion of 126 orgs/100 ml. Seventeen of the combined 24 samples (71%) exceeded Iowa’s Class A1 single-sample maximum criterion of 235 orgs/100 ml. According to U.S. EPA guidelines for Section 305(b) reporting and Iowa DNR’s assessment/listing methodology, if the geometric mean is greater than 126 orgs/100 ml., the primary contact recreation uses should be assessed as "impaired" (see pgs 3-33 to 3-35 of U.S. EPA 1997b). Thus, because at least one recreation season geometric mean exceeded criteria for Class A1 uses, these uses are assessed as "not supported."

Results of chemical/physical water quality monitoring at DNR station 10520001 near Iowa City suggest “full support” of the aquatic life uses. Monitoring showed no violations of Class B(WW2) water quality criteria for 35 Ammonia samples (maximum = 1.7 mg/L), 36 Dissolved Oxygen samples (minimum = 5.2 mg/L), 35 pH samples (range = 6.7 to 8.4), 36 Temperature samples (maximum = 27.5°C), 36 Chloride samples (maximum = 92 mg/L), or 36 Sulfate samples (maximum = 95 mg/L) occurred during monitoring from January 2014 to December 2016. According to U.S. EPA guidelines for Section 305(b) water quality assessments (U.S. EPA 1997b, page 3-17), the EPA guidelines allow up to 10% violations of these conventional parameters before impairment of water quality is indicated. Thus, these results thus suggest “full support” of the Class B(WW2) aquatic life uses.

This aquatic life assessment is now considered "evaluated" based on a change in the 2010 DNR assessment methodology. DNR now requires a segment have two or more biological samples collected from the segment in multiple years over a recent five-year period to be considered “monitored”. This segment had multiple samples collected in the previous seven years (2010-2016); however, the multiple samples were not collected during a five-year period. According to DNR’s assessment/listing methodology, impairments based on “evaluated” assessments are of lesser confidence and are thus not appropriate for Section 303(d) listing (Category 5 of the Integrated Report). DNR does, however, consider these impairments as appropriate for listing under either Category 2b or 3b of the Integrated Report (waters potentially impaired and in need of further investigation). However, despite this change in assessment methodology and type, this waterbody remains in IR Category 5b-t and remains on Iowa’s Section 303(d) list of impaired waters.